Soybean Phytophthora Root Rot Survey
Dale Baird, Extension Educator Crop Systems, Rockford
Extension Center, 815-397-7714, firstname.lastname@example.org
Soybean Phytophthora Root Rot (PRR) disease has become more common
throughout the Midwest during the past five years. PRR is caused
by a soilborne pathogen that has been kept in check in the past
with PRR resistant or tolerant varieties. PRR resistant soybean
varieties contain resistant genes or Rps genes that trigger the
production of an antifungal compound in soybeans. Forty-five different
races or strains of PRR have been identified, but not all races
have been confirmed in Illinois. The Rps1-k gene controls several
common PRR races and is the most widely used Rps resistance gene
in commercial varieties. However, the Rps1-k gene is not effective
against several of the "new" PRR races confirmed in
the Midwest during the 1990s.
Dr. Dean Malvick, University of Illinois Extension plant pathologist
has initiated a PRR Survey. The survey objective is to isolate
and identify possibly new PRR races in Illinois. If you suspect
you have PRR in 2002 or have a field that has a history of PRR
infection contact your local Extension office. A Crops or IPM
Educator will collect soil and plant samples and forward them
to Dr. Malvick for potential race isolation.
Seedling stage PRR is characterized by a bruised, soft, brown
root rot before emergence or shortly after emergence. PRR at the
seedling stage can easily be confused with Pythium or Rhizoctonia.
Rhizoctonia can be confirmed by observing a reddish lesion on
the root. Later season PRR is characterized by yellow, wilting
and dying soybean plants. On closer inspection usually a distinct
dark brown discoloration can be observed on the plant stem that
extends upward from the soil line.